#define _CRT_SECURE_NO_WARNINGS 1
//1 1 2 3 5 8 
//a b c=a+b
//  a b 
#include<stdio.h>
int fib(int n)
{
	int a = 1, b = 1;
	int c = 0;
	while (n > 2)
	{
		c = a + b;
		a = b;
		b = c;
		n--;
	}
	return b;
}
int main()
{
	int n=0, ret=0;
	scanf("%d", &n);
    ret = fib(n);
	printf("%d", ret);
	return 0;
}